Underp ReleephDefaultFieldSelector

Summary: Oops. Functions only return stuff when you call the return() function on the lvalue.

Test Plan: Use ReleephDefaultFieldSelector is the field selector in a test Releeph project.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5362